1. Field of the Invention
The present invention relates generally to a lens, and more particularly to a zoom lens.
2. Description of the Related Art
With advancement in technology, image devices, such as camera, video camera, microscope, and scanner, are made smaller and lighter for portability and operation that the zoom lenses incorporated in such image devices have to reduce its size. Except that, the zoom lenses must have high optical performance, such as high zoom ratio, high resolution, and high contrast. Therefore, small size and high optical performance are the important facts of the modern zoom lenses.
In order to raise the zoom ratio and the optical performance, more and more lens groups are provided in the zoom lens. As we know, some zoom lenses have six lens groups or more, and the totally lenses of the lens groups are more than twenty. It is obvious that more lens groups will cause the zoom lens bigger and heavier. However, when the zoom lens has fewer lens groups, it may have a small size, but the optical performance is poor.
Therefore, the conventional zoom lens still needs to be improved.